1. Field of the Invention
The present invention relates generally to fluid dispensing apparatus. More particularly, the invention concerns a medicament delivery device for dispensing medicinal fluids to ambulatory patients that includes a novel stored energy source in the form of a variable force spring. The variable force spring is cooperatively associated with the collapsible reservoir of the device and functions to deliver a variable force to the reservoir that tends to urge fluid flow therefrom at a substantially constant rate. In the preferred form of the invention the stored energy source uniquely comprises an elongated, pre-stressed strip of spring material that is formed into coils and exhibits a cross-sectional mass that varies along its length.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
A number of different types of medicament dispensers for dispensing medicaments to ambulatory patients have been suggested in the past. Many of the devices or apparatus seek either to improve or to replace the traditional gravity flow and hypodermic syringe methods which have been the standard for delivery of liquid medicaments for many years.
The prior art gravity flow methods typically involve the use of intravenous administration sets and the familiar flexible solution bag suspended above the patient. Such gravametric methods are cumbersome, imprecise and require bed confinement of the patient. Periodic monitoring of the apparatus by the nurse or doctor is required to detect malfunctions of the infusion apparatus. Accordingly, the prior art devices or apparatus are not well suited for use in those instances where the patient must be transported to a remote facility for treatment.
With regard to the prior art, one of the most versatile and unique fluid delivery apparatus developed in recent years is that developed by one of the present inventors and described in U.S. Pat. No. 5,205,820. The components of this novel fluid delivery apparatus generally include: a base assembly, an elastomeric membrane serving as a stored energy means, fluid flow channels for filling and delivery, flow control means, a cover, and an ullage which comprises a part of the base assembly.
Another prior art patent issued to one of the present applicants, namely U.S. Pat. No. 5,743,879, discloses an injectable medicament dispenser for use in controllably dispensing fluid medicaments such as insulin, anti-infectives, analgesics, oncolylotics, cardiac drugs, bio-pharmaceuticals, and the like from a pre-filled container at a uniform rate. The dispenser, which is quite dissimilar in construction and operation from that of the present invention, includes a stored energy source in the form of a compressively deformable, polymeric, elastomeric member that provides the force necessary to controllably discharge the medicament from a pre-filled container, which is housed within the body of the apparatus. After having been deformed, the polymeric, elastomeric member will return to its starting configuration in a highly predictable manner.